Variable displacement pump and motor



Get. 11, 1949. M. F. HILL ET AL VARIABLE DISPLACEMENT PUMP AND MOTOR 5 Sheets-Sheet 1 Filed April 15, 19%

4 M. F. HILL ET AL 2,484,379

I VARIABLE DISPLACEMENT PUMP AND MOTOR Filed April 15, 1944 5 Sheets-Sheet 5 INVENTOR5 Mwwm FHILL mamas ILHILLZM .rm-m L. CHEF/MN- BY, gim

ATTORNEY Oct, 11, 19490, M. F. HILL ET AL 2,484,789

VARIABLE DISPLACEMENT PUMP AND MOTOR Filed April 15, 1944 5 Sheets-Sheet 4 lflveyfrbns MYRONfiHlLL FRANCIS R.HlLl ,Zm:-

ATT'Y @Qt 11, 194%. M. HELL ET AL 2,484,789

VARIABLE DISPLACEMENT PUMP AND MOTOR Filed April 15, 1.9% ,5 Sheets-Sheet 5 gin/0mm Mwva v. K H/LL FHA/V615 HILL 2 m Jo HN. L CA/AH/v, M

Patented Oct. 11, 1949 VARIABLE DISPLACEMENT PUMP AND MOTOR Myron F.

Hill and Francis A. Hill, 2nd, Westport, and John L. Chapin, Jr., Wilton, Conn.,

asslrnors to Hill Laboratory, Myron F. Hill, proprietor,

Westport, Conn.

Application April 15, 1944, Serial No; 531,266 19 Claims. (01. 103-120) Our invention relates to variabl displacement pumps and motors. The problem of the proper construction for a. satisfactory variable displacement motor and pump has been a difilcult one for many years.

The field has been occupied perhaps entirely by pumps of the Dowty or Hele-Shaw type, composed of a plurality of cylinders, the pistons of which through connecting rods or plungers exerted a thrust on an eccentric arm, usually in a radial direction from the drive shaft. Such mechanisms make excellent pumps, but motors fail to operate when the eccentric arm approaches zero. The pressure area of the pistons is constant, and to vary the displacement, the eccentricity i reduced, it being the crank arm. At zero displacement, it is like an engine piston trying to rotate the shaft by exerting thrust upon the dead center. As a pump however it is most efficient.

The many parts, the great precision of manufacture, and the resulting cost of manufacture have encouraged rotary pump inventors to try to make a rotary pump do the same work because of its fewer parts and lower cost. The principle of telescoping parts has received attention, in order to reduce displacement, instead of reducing the crank arm or the eccentricity. Rotary pumps and hydraulic rotary motors depend for their efficiency upon tightly fitted, free running rotor members there being no piston rings. There are usually two rotors in double gear pumps and internal gear pumps.

Internal gear pumps or motors of the crescent variety, in which crescents at open mesh fill in the vacancy between the teeth, have not been employed because of the difficulty imposed by the crescent, which prevents the telescoping action.

Telescoping double gear pumpshave been inventedsee Patent No. 1,742,215 of 1930. But the same inventor later by-passed that faulty the difficulties due to production manufacture, where tolerances, or allowable variations in assembled members, is a generally accepted principle. The telescoping parts having their own tolerances have to be so made as to fit on members of the largest tolerance sizes, and when on membersof the least tolerance, the leakage may be as much as four times that of pumps without telescoping members. The lack of such units in commercial use indicates their failure to solve the problem.

Our fitted bulkhead, or slidable end wall of a rotor chamber, moulded to a rotor, has solved this leakage problem; and other novel construction enables the mechanism to act as a motor from approximately zero displacement up to the maximum, something that is lacking in the Dowty and Hele-Shaw form. It acts as a motor, pump or meter with equal efliciency, and has other advantages.

Bulkheads machined to exactly fit the teeth of rotors have been attractive as a solution. But imagine the difficulties, mechanically, of first indexing the mated tooth forms, of-arriving at their exact tooth contours-of various radii, inverted; their exact diameters, all to be rendered useless by the principles of tolerances in manufacture. Experienced mechanics would baulk at even trying to do it. Such bulkheads (called spiders) were shown in Patent No. 1,742,215 above referred to and were abandoned.

Our solution is die-casting or moulding onto or into rotors a bulkhead, which while it is slidable on its rotor, is so tight fitting around the tooth contours as to prevent leakage. If the various factors vary in manufacture due to tolerances, it makes no difierence, since each bulkhead is made on or in the rotor which it is intended to serve construction in favor of the internal gear type,

see Patent No. 1,990,750 of 1935, using the rotors under the patent to M. F. Hill, No, 1,682,563 of 1928, where the continuous contact at steady speed between the teeth rendered the crescents unnecessary.

In these telescoping mechanisms, the problem of excessive leakage arose. The leakage between the ends of rotors and the side Walls, where piston rings cannot be used, is bad enough, often up to 15% under some production conditions, but the addition of leakage between the tops of the teeth and telescoping recesses in bulkheads causes a prohibitive loss for the high pressures used in variable pumps. The leakage problem is tied to thereafter and conforms to its exact size. Thus each rotor always carries its mated bulkhead. Fluid under pressure in a rotor chamber cannot escape under a bulkhead to' reach the leakage area between the end of its rotor and the adjoining sidewall. Thus one half of the leakage area of ordinary motors and pumps is eliminated. The bulkhead does not revolve on its rotor but is mounted on and supported by its teeth. The only wear that can occur is through the endwise slide of the bulkhead. As this is occasional, the fit on the teeth is practically permanent.

Moreover, the bulkhead is composed preferably of a. thermosetting plastic composed of graphite, strength fibers, and a bond which so changes its chemical composition at its setting temperature of 300 to 400 F. and 600 to 800 lbs. or more pressure per square inch, that the plastic has tensile strength and toughness many times that necessary for its bulkhead work. Its elasticity is high and its follows the expansion and contraction of metals to which it is bonded in the ranges of temperature of normalservice.

The great advantage of this plastic is its antifriction quality, its graphitic content, 20% to 40%, providing slipperiness. As a motor, such a mechanism can run with non-lubricating liquid, and, driven by a dry gas, even run with no liquid at all, when the bulkheads are in close proximity to each other. It is conductor of heat and is capable of withstanding bearing temperature. Be-' in slippery it cannot seize as metals do. A motor so made has high volumetric and overall efllciency.

The teeth of internal gears that use the bulkheads have smooth tooth contours that do not cut or tear the bulkhead material, and that permit the sliding action of the bulkheads on them. The bulkheads are molded to their respective rotors to fit the radially disposed teeth of the gears or rotors so that the bulkheads are mounted upon and supported by the teeth and therefore turn with the teeth. The radial tooth portions of a, bulkhead fitting into th tooth spaces of the gears or rotors are supported or carried by the annular wall of bulkhead construction which also acts as an end wall of rotor chambers. The bulkhead fitting the outer rotor for example has its tooth portions upon the wall portion, which wall portion extends radially outward from them. The wall portion constitutes an end wall of a rotor chamber. Similarly th bulkhead molded to the pinion rotor has inwardly extending bulkhead tooth portions fitting the tooth spaces of the pinion. These tooth portions are supported and held in place by the wall portions extending radially outward from them, which wall portions constitute the other end wall of the rotor chambers. The same bulkhead portions thus perform different functions. If rotor curves are manufactured with high precision the bulkheads and rotors become interchangeable, and standardized moulding forms become Possible. These telescopic bulkheads are the solution of this problem. v

When a telescoping member or bulkhead is moulded to fit the teeth of a rotor, a free sliding action between the two is needed. If the fit is too tight they may be put into a machine or contrivance to reciprocate the rotorback and forth on or in its bulkhead to give it the freedom required for easy operation. Oil, charged with flour of sulphur, Bpn Ami, or rouge, will assist.

this operation. It may be combined-with runmng-in or testing the pump in an oil circuit before sale.

The preferred plastic is-composed of the finest flour of. graphite, with thin filaments or fibres, flat or rounded, of material of the order of paper, cotton; glass. or plastic having tensile strength, bonded with a suitable phenol resin. At 300 to 400 F. and a hydraulic pressure of six to eight hundred pounds (or more) per square inch, this compound sets, and maintains tight relations with rotors made of any suitable material. Its tensile, shear and compression factors are many times as high as the work requires. Graphite gives it antifriction qualities even when dry. Its elasticity factor permits it to be bonded to steel and other metals at a thermosetting temperature. The union is not disturbed when cooled back to normal, nor by expansion and contraction at normal temperatures of use.

Assembly of the rotors, with their bulkheads, in a suitable casing provides a unit, which, receiving oil under pressure, may be manipulated to vary its shaft speed from zero revolutions per minute to that obtainable from its maximum capacity: It may be set while running to receive or deliver any desired constant volume of fluid. Operated as a pump at steady speed it may deliver from nothing to its maximum capacity.

It is the length of the teeth of the rotors between the bulkheads one of which may slide toward the other until it touches it, that varies the displacement. When it is at zero, the unit becomes a shut-oil valve. At this moment a reversing valve may reverse the flow through the rotors without shock, the intake port becoming the discharge port and vice versa, 50 that the mechanism may begin its functioning in the opposite direction.

For machine tools this is advantageous'as a bulkhead may be caused to slide in either direction by controlling devices for driving fast, or slow or for stopping. As a pump it is similarly useful.

The continuous contact type of tooth curve is described in our Patents No. 1,684,563; Reissue No. 21,316; No. 2,209,201, and in others. We prefer the Rotoid (see last patent) type as the best, which for a given diameter has greater displacement than Gerotors (see reissue patent above). Gerotors have a difference of one tooth while Rotoids have a diiference of two teeth. For six .outer teeth Rotoids have forty percent greater displacement than Gerotors, and driving angles from 0 to 17 instead of the 30 to 50 of Gerotors, Both have continuous contacts between their teeth at steady speeds. No crescent insert is needed, in the open space at open mesh in Rotoids, and Gerotors have no open located around the outer space. Hence both are adapted to the bulkhead construction for variable displacement. As a motor, Rotoids with their superior pressure angles and greater (eccentric) power arm are preferable to Gerotors.

When full open one shiftable bulkhead, moulded in the outer gear or rotor, may be located at an end of the pinion or in a groove in the pinion around the shaft, and the other shiftable bulkhead moulded on the pinion may be located at the end of the annular or outer gear or rotor, where the pinion may be caused to slide through it, until the bulkheads meet. The portions of the gear teeth in mesh between the bulkheads perform the displacement functions, as a motor or otherwise.

An obstacle in Gerotors to successful use as motors has been the clutching action between the outer rotor and its bearing in the casing. Compared to the shaft bearings, this outer bearing is large in diameter. Such mechanisms have refused to work when subjected to as high as a thousand pounds of oil pressure; It seems that the pressure causes the outer rotor to cling tightly to its bearing, and its friction and clutching action prevent starting. Roller bearings have been used with success to overcome this defect, but rotor, they increase the size of the mechanism out of all proportion. Needle bearings help start the unit but at the speeds usually desired for either motors or pumps of this type, they do not roll.

This outer bearing, when made of plastic, alleviates this obstacle, since the graphite in the plastic is slippery. With such an outer bearing, the casing may be of normal size and the least fluid pressure starts rotation of Rotoids wtih their low pressure angles. After once starting, the lubricant is swept into the bearing areas and rotation is impeded only by slight oil friction. Each outer rotor tooth space may be vented by a hole to the outer bearing areas to balance outward radial pressure. Molding eliminates much of the cost of machining, and is light in weight. Its specific gravity, around 1.5, makes it ideal for aircraft purposes. I Y

In the drawings:

Figure I is a vertical IV.

Fig. II is a section of the bulkhead and pinion as the same would appear when viewed along line 11-11 of Fig. I.

Fig. III is a section of a companion bulkhead and associated pinion as the same appears when viewed along line III--III, Fig. I.

Fig. IV is a section on line IV-IV, Fig. I.

Fig. V shows a detail.

Fig. VI is a view of the casing partly in section, showing the slidable pinion and bulkhead between them in elevation, the other bulkhead being in section.

Fig. VII is part diagram and part elevation of a reversing valve.

Fig. VIII is a detail.

Fig. IX is a section of a Gerotor fluid displacement mechanism in which the numbers of teeth differ by one. It is taken on line IX-IX, Fig. XI.

Fig. X is a section of the casing on line X=X, Fig. XI, the rotor movement being shown in elevation.

Fig. XI is a section of Fig. IX on line XI-XI.

Fig. XII is an end elevation showing the four way valve attached to the displacement mechamsrn.

Fig. XlII is a section of Fig. IX on line XIII- XIII.

Fig. XIV shows the shape of a, bulkhead in Fig. IX for fitting the outer rotor.

Fig. XV shows the shape of a fits the inner rotor in Fig. IX.

Fig. XVI is a section of the check valves in Fig. X, one valve for each port that maintains low pressure in the casing.

Fig. XVII is a section of Fig. XVI on line XVII-XVII.

Figs. XVIII and XIX are diagrammatic views.

Figs. XX and XXI are perspective views of mechanisms in Fig. I.

In the drawings, our invention includes a pair of internal rotors or gears suitable for displacement purposes, one eccentric to the other and having a difference of a plurality of teeth, in this case a difference of two, and their mated bulkheads. The pinion rotor I has its mated bulkhead 2, located at the end of the outer rotor 3 which in turn has its mated bulkhead 4, located between the two pinion parts I and la.

The rotors have eleven and thirteen teeth (a ratio, of 5 /2 to 6 /2) forming chambers, as shown in Fig. IV, which open and close during the performance of fluid pressure functions. This difference in the numbers of teeth is not a matter of degree since a difierence of two teeth gives greater displacement than a difierence of one tooth and even of three teeth.

The pinion axis is at 5 and the outer rotor axis is at 6, the distance between them being the'eccentricity. It is also the length of the power arm of the motor, and is a fixed factor, regardless of the areas of tooth pressure involved as a motor.

In the fact of driving the shaft for performsection on line l-l, Fig.

bulkhead that ance of work the pinion is keyed to the shaft and their speed depends on the fluid pressure. and the work to be done. The outer rotor is not impeded by an load except helping to drive the pinion, and therefore engages the teeth of the pinion to help it turn. For example, fluid pressure entering the casing at I enters the rotor inlet holes 8 as they pass by the port 9, causing the pinion to turn clockwise. The tooth engage- ,ment between the rotors is where the chambers are closing and releasing the fluid out through the holes 8 into the port In and exit II. The teeth are provided with back lash enough to be out of contact along the port 9, so that pressure fills all chambers that do not connect with the outlet port 10. This differential of pressure causes rotation. The chambers, at their ends, are closed by the bulkheads. The location of the pinion bulkhead 2 is between the rotor 3 and the side wall to.

The outer rotor has a bearing 12 in a ring it. This bearing 12 is also of plastic, providing an antifriction efiect. The ports 9 and III are cut through this bearing. This lining of plastic may be moulded directly into the ring 93, the interior metal surface being rough machined with a pointed tool. With a resin bonding agent applied to this machined surface before moulding the plastic clings to it so tenacicusly as to be removable only in fragments. The holes 8 transmit fluid pressures inside of the rotor to its outside surface, thus establishing a balancing pressure tending to float the outer rotor in its bearing. The bulkhead 8 of this outer rotor rotates with it of course, and is confined endwise between the two sections l and la of the pinion. It has a. hole It large enough to clear the shaft it as indicated in Fig. II.

If the shaft travels at 1300 R. P. M. the pinion travels at the same speed. The outer rotor however having 13 teeth, travels at /1: of 1300, or 1100, thus travelling at 200 R. P. M. slower than the pinion.

The pinion i is keyed to the shaft by means of a key It, which also keys the end portion in to the shaft. This key has end lugs II and it between which the pinion portions i and is are confined, leaving room for the bulkhead 3 and the shoulder l9 on the operating sleeve 28. This sleeve pulls the key I6 to the right in Fig. I and pushes the pinion assembly to the left for the purpose of sliding the, bulkhead d in the outer rotor 3. The sleeve 20 has the key slot 25 slidable on the pin 22 as the screw 23 turns in the end 2 3 of the sleeve. This sleeve is journalled in the casing 25 snugiy and is lined with plastic 28 for the shaft L5 to run in. The screw 23 has the enlargement 21 between the sleeve end 2% and the screw cap 28 to prevent its endwise displacement. An operating button 29 is pinned to the screw to turn it with. Additional keys 3E3 (Fig. III) assist the endwise sliding operation. The key slots extend sufficiently-to accommodate the endwise movement desired. In this form the bulkhead A is to slide until it touches bulkhead 2, when the displacement is zero. This means that the right-hand end of the pinion member i reaches the left-hand end of the annular memher 3 losing tooth engagement. The pinion member Ia however maintains enough tooth engagement to keep the member I registered with 3 for tooth reengagement when the bulkheads are again separated. The member in acts only as a gear, having no displacement functions.

The shaft it has another groove 31 acting as a fluid duct between the chambers 32 and 33 to permit hydraulic endwise freedom. The space 34 is connected to space 32 through the hole 35,

. key way slot 2|, and a slot 36, also for hydraulic freedom, oil flowing back and forth as needed through these slots as the screw 23 advances or retracts the pinion assembly and th bulkh 4 carried by it.

To avoid the bulkhead 4 as it approaches bulkhead 2, from blocking off th holes 8 in the middle of the outer rotor 3, the holes are extended as indicated at 31 (Figs. I and II), so that they are never disconnected from the rotor chambers while performing displacement functions, as the latter taper off to nothing.

The shaft has the collar 38 running against the plastic surface lining moulded into the casing member 39 as indicated at 40. The oil seal has the cap 4|, which may be of Bakelite, running against the lining 40. A spring Ma exerts the needed pressure. The cap 4| is mounted on a rubber (for water) or neoprene (for oil) sleeve 42 which is stretch fitted to the shaft and compression fitted in the cap, and which has suflicient resiliency and elasticity to leave the cap fill free to lie fiat against the lining 40 to prevent leakage between them. The lining is preferably moulded into the casting, even without machining the casting if desired. The shaft has a collar 43 resting against the lining 4|]. The collar 43, which may be a pulley, is keyed at 53a to the shaft, the key being engaged by set screw 43b in the collar. The collar 43 and the collar 38 prevent endwise displacement of the shaft.

Indicating one possible form of connection of the shaft to its work, the collar 43 may be a pulley for belt drive.

The oil filled spaces 32, 33 and 33 may have low pressure and are therefore kept in connection with low pressure port passageways. This is accomplished by a check valve from each port passageway closed when that port is at high pressure and open otherwise. Such a device is shown in Fig. V, the ball check 44 in casing member 39, connected to the port 10 for example by the hole 45 and to the space 33 by the hole 46. If the port Ill contains high pressure it thrusts the ball against its seat. If at low pressure, any higher pressure in 33 pushes the ball aside so that pressure is relieved.

Fig. VII shows the motor reversing circuit. When the motor M has been running in one direction (either one) and the bulkheads are brought together, all exertion of power in that direction has ceased. At this moment conditions favor reversal which is accomplished by turning the handle 41 of the four-Way valve V some 90 which reverses the connections of the ports 9 and ID to the source of power 0 and the sump S. After reversal of the valve, the slightest separation of the bulkheads provides tooth area which initiates pressure upon the power arm which is equal to the eccentricity of the rotors and as soon as this pressure is enough to overcome inertia, rotation is started. Without this reversal at zero displacement, a sudden pressure in the nature vof a shock would cause a jumpy action and prevent close motor control.

While we have disclosed our invention as a hydraulic motor, it is obvious that it may operate by gas pressures, and that it may operate also as a pump, compressor, meter, and similar devices.

It may be set for different permanent displacements, and also be varied during operation to receive or deliver desired volumes.

As a motor, its low pressure angles of drive between the teeth relieve outward clutching pressures. Its antifriction bearings and its fixed power arm insure free application of minimum fluid pressures for creating torque from zero displacement. And its moulded bulkheads create a fluid tight construction having high v01- umetrio efliciency.

In Figs. VI and VIII, the window 48 in the casing member 25 and the arrow t9 marked on the sliding operating member 20 indicate the setting of the bulkheads, while the scale interprets the displacement in gallons per minute at usual speed of 1725 R. P. M.

Fig. IX shows our bulkheads applied to another internal gear construction in which there is no crescent. The teeth make continuous contact at steady speed, as described in Reissue Patent No. 21,316 to M. F. Hill.

The casing members 50 and 5| bolted together upon the meeting line 52 enclose the variable displacement rotors 53 and 54 with their bulkheads 55, 56 respectively moulded to them, as in the Rotoid construction above described. The rotor 53 has its extension 53a keyed in registra- 0 tion with it by the key 57. A member 58 similar to a key except for the key slot in the rotor 53, 53a, is added to assist in endwise adjustment for variable capacity, the rotors, bulkhead 5E and shoulder of the operating member 59 being fitted nicely between the upturned ends of members 51 and 58.

The outer rotor 54 is journalled in the plastic bushing 60. One end of the operating shaft 6| is journalled in a similar bushing 62, the other end of the shaft being journalled in a similar bushing 53. A sponge rubber ring 64 adheres to the shaft and its Bakelite or other cap 640. runs against an extension of the bushing 63. A spring 65 between the driven pulley 66, keyed to the shaft, and the cap 64a causes these members to be a tight durable seal. Any other driving can be used instead of the pulley.

The bulkhead 55, as shown in Fig. IX has one end carried by the teeth of the pinion 53 and the other end resting upon the shoulder 61 of the shaft all of which rotate together.

The operating screw 68 is threaded to the member 59 and as it is unscrewed pushes 59 to the left. It in turn pushes the pinion assembly along the shaft carrying the bulkhead 56 toward the bulkhead 55 until they touch, at which time shaft rotation ceases. At this moment the valve V may be reversed, so that oil supply, assumed to be at constant pressure, enters the opposite part of the motor. .As the bulkheads are pulled apart by screwing up on the screw 68, pressure starts the motor in the opposite direction. If there is a load upon the shaft, it stops slowly as volume drops off to zero and starts slowly. These functions and operations may be varied by differing oil pressures and loads.

Fig. X shows these internal members in elevation, and Figs. XI and XIII show them more or less in section.

If it is desired to maintain low pressure outside of the rotor chambers, the check valves 69 and HI prevent high pressure from escaping from the ports and permit any rising pressure to escape into the port which is at low pressure. I

The pressure in the rotor chambers tending to force the bulkhead 56 away from 55 is resisted by the pinion member 53a which in turn is pushed against the upturned ends of the key members 51 andv 58. As these parts rotate together (except 9 the bulkhead) there is no wear as of runnin parts. The speed of the bulkhead 56 with relation to the pinion 53a is as 1 to 8. The bulkhead has a tough slippery surface and if it runs against a polished rotor end surface, its wear is so slight as to be of no consequence.

The pin 10a prevents the memberiS from rotating.

Fig. XIV shows a side view of an outer rotor bulkhead, and XV of a pinion bulkhead.

The holes 'II in the outer rotor connect the rotor chambers to the ports until the bulkheads come together for zero displacement.

The method of laying out the tooth contours of rotors having a difference of two teeth is illustrated in Fig. XIX.

From a central point Y a circle E is described. the radius of which is equal to the eccentricity selected for the prospective rotor curves.

Another circle Z is described from the center Y, the radius of which is equal to the number of teeth of the pinion divided by two. multiplied by the eccentricity. A ratio of 9 to 11 teeth, shown in Fig. XVIII. is selected for this diagram for simplicity. Other various ratios having numbers of continuous contact teeth differing by a plurality. can be used.

Both circles for convenience are divided into ten equal parts, and for intermediate curve regions each part might be further subdivided on both circles. The dividing points on the drawing are numbered as far as 5, the other points not being involved. such as I, 2, 3, 4, and 5.

A rolling circle, or a part of it, A is illustrated, tangent at the point to Z. A radius R of this circle A is drawn from its center point 0 on E to its point 0 on Z and A and extended to selected outside point 0 as shown in curve C.

With these factors to start with, points of a cycloid are locatedat the successive corresponding positions of the end of radius 0-0-0, termed the radicroid coined from radius of a circroid," then points for a trochoidal curve C are located. The curve C is called for convenience a circroid! The intersection of normals from the circroid, to the points on the ratio circle Z where A is successively tangent, is then found, and finally the character of the rotor tooth contours is determined. The radius li-0-ii is termed the radicroid, a word coined from the phrase radius of a circroid. Thus there are four stages of geometrical development necessary to establish a conti ous tooth contact between engaging gear or rotor teeth. Now by rolling the circle A on the circle Z, the point 0 in A describes half a cycloid L, shown in part thru points I, 2, 3, 4 and 5. To lay of! this half cycloid, or a succession of points thru which it extends, the circle A is shown in successive positions during rolling. A second position at l on Z locates point I of the proposed cycloid. To locate this point I, the distance i to 0 on Z is laid ofl as ll on this circle A in its second position. In this second position the circle or are A is tangent to the ratio circle Z at its point i. The chord from i on Z to i on L is therefore an instant radius of the cycloid and therefore normal to the cycloid.

The circle A is rolled to another position tangent to Z at its point 2, and two such chord lengths are laid off on A in its new position, thus locating the point 2 of the cycloid.

This process is repeated with other successive positions on A numbered 3, l and 5. Other intermediate positions between i and 3 are of asany 10 isiitance in critical curve relations as referred to a er.

The radius of A, extended from II on E thru 0 on A, to 0 on C, forms the radicroid. When the circle A is tangent to Z at I, the radicroid extends from I in E thru the point i in the cycloid to I in C. When tangent to Z at 2, 3, 4 and 5, the radicroid extends from 2, 3, 4. and 5 in E, thru the same points 2, 3, 4 and 5 respectively of the cycloid L, to the similarly numbered points 2, 3, 4 and 5 in C, respectively.

This radicroid has a definite assumed length. The circroid located at C is dependent on the length of v the radicroid. This length may be varied at will, and rotor curves established in accordance therewith. For the nine to eleven tooth rotors, the length shown is convenient so that the outer tip of the radiocroid describes circroid C, travelling thru the successive points of C that correspond with the similar points on the circles E and Z and on the cycloid L.

The next factor to determine is how far from this circroid may a rotor curve lie, and be parallel to it. A circular arc as a master form is the easiest to handle and understand.

Various normals are drawn from C to discover where they intersect. If the chord of A, from i on Z to l of the cycloid, which is the instant radius of the cycloid and normal to it, is extended to C, it is also the instant radius of C and normal to it.

Lines drawn from the tangent points on Z to the corresponding successive points on C are also normals to C because the circle A is pivoting upon the successive points of Z and the tip of the radicroid, being integral with and carried by the circle A, is one end of an instant radius in every successive position.

Lines drawn from the points on the circroid to corresponding points on the circle Z, being these instant radii, are the normals to the circroid.

The points of their intersections nearest to the circroid is indicated at N.

To lay off a tooth curve, arcs are described centered at successive points on the circroid thus outlining a curve of envelopment HG. If HG is to the left of the point N, as at F, undercuts will occur. A tooth having the radius of "curvature shown at F, would have a sharp corner, a safe indication that after it was established from a center 2 on C it would cut it back from a center 3 on C, whereas if GH is to the right of N it describes by envelopment a forwardly extending contour all the time that its center travels along C. In Fig. XVIII GH is also shown. The other side of the tooth is the same in reverse as shown in Fig. XVIII, at KP.

The next step is to select the portion desired for a tooth curve. The efiective tooth curve of the outer rotor is the are having the radius that outlines GH.

A tooth of a nine tooth .pinion extends 40 around the ratio circle Z. One side of a tooth and tooth space therefore extends 20.

By drawing lines G and H to Y, having a spread of 20, an effective pinion tooth contour may be selected. These lines may be swung (together) to the right or left around the center Y, to pick out the contour that is best for the pinion. In the position shown the selected contour extends from G to H, thereby determining the outside and inside diameters of the tooth contours of the pinion shown in Fig. XVIII. The other side of the tooth as Kl? is of course the reverse of GH. This also determines, by adding the eccentricity, the radii and inside or outside diameters of the teeth of the outer rotor. This is the epi system of generation. Generation may be reversed into a hypo" system as in Patent No. 1,682,563, but the curves are so poor and diameters so enlarged for a given displacement, they are not so advantageous. However, they lie within the scope of our invention.

While we have described specific curves. and

- contours for teeth, it is understood many variations may occur from those shown and specifically described without departing from the principle of continuous contact between rotors and gears having a tooth ratio of fractional numbers having a difference of one.

It is of course obvious and understood that the invention is not limited to the precise structure shown and described since the invention is capable of various modifications within the scope of the claims. Also it is not necessary to employ all of the elements as they may be used conjointly or in any combination desired. Furthermore the invention is applicable to motors, compressors, pumps, meters and any other device where a fluid, either liquids, gases or other mediums are to be subjected to energy transfer, work translation, physical changes, etc.

What we claim is:

1. In combination, in a casing. a fluid mechanism comprising toothed displacement members, one within and eccentric to the other and having teeth differing in number by two, said teeth having a ratio of fractional numbers difiering by one, said teeth forming rotor chambers between them, said chambers being sealed from each other during rotation by continuous tooth contacts while performing displacement functions during intake and outlet, passageways for the intake and outlet of fluids, said passageways located radially thru the outer rotor andin said casing, an individual bulkhead moulded to the teeth of each rotor, said bulkheads forming end walls of said rotor chambers, one bulkhead being slidable with respect to its rotor, and cooperating with said passageways to vary the displacement of said chambers, said bulkheads being formed of a thermo-setting hardened plastic material with radial projections entering the tooth spaces of said rotors, and a journal bushing for said outer rotor of slippery material to facilitate starting said rotors under high fluid inlet pressure.

2. In a fluid mechanism, rotary toothed displacement members, one eccentric to the other, the teeth of said members forming chambers between them which open and close during rotation, a bulkhead fitting and sliding upon the teeth of each member, said bulkheads including radial portions extending into the spaces between the teeth of said displacement members, said radial portions being supported by radially extending walls enclosing said chambers at their ends, and means to slide one bulkhead towards and away from the other bulkhead to vary the displacement of said rotor chambers.

3. The combination claimed in claim 2 having means extending into said mechanism thru one of its walls, engaging said one of said bulkheads to increase and decrease displacement in said rotor chambers.

4. In a fluid mechanism, toothed rotary displacement members, one eccentric to the other, the teeth of said members forming rotor chambers which open and close during rotation, a hard fluid pressure-holding bulkhead moulded to the teeth of each rotor member, each bulkhead bein volume, each bulkhead having radially extending.

tooth members fitting and sliding upon the teeth of said displacement members, each bulkhead having radial wall portions carrying said radially extending tooth members.

5. The combination in claim 4 wherein one rotor is within the other.

6. The combination in claim 4 wherein one rotor is within the other and has a difference of a plurality of teeth.

7. The combination in claim 4 wherein slippery antifriction thermosetting bearing bushings are moulded to said casing under heat and pressure.

8. The combination in claim2wherein one bulkhead is located between two portions of one rotary toothed member, whereby one of said portions does, and the other does not perform displacement functions.

9. The combination in claim 2 wherein one bulkhead is located between the two ends of one rotary toothed member, and the other bulkhead is located at one end of the other rotary toothed member.

10. The combination in claim 2 having a casing, an intake and outlet port, and a space at one end of said displacement members to receive a telescoping member; spaces at the other end of said displacement members to receive a telescoping member and valve means to maintain even hydraulic pressures in said spaces, said valve means comprising check valves in ducts between said spaces and ports arranged to prevent fluid flow from said ports, and permit fluid flow to said ports, whereby the pressure in said spaces conforms to said port having the lower pressure.

11. In combination, a fluid displacement mechanism comprising toothed rotors, one within and eccentric to the other and having teeth differing in number by at least one, forming rotor chambers between them sealed from each other during rotation by continuous tooth engagements while performing displacement functions during fluid intake an outlet and an individual bulkhead moulded to the teeth of each rotor whereby leakages due to tolerances of manufacture are eliminated, said bulkheads forming end walls of said rotor chambers, one bulkhead having radially projecting tooth portions fitting and slidable with respect to its rotor and traveling axially with the other rotor, to vary the distance between said bulkheads forming the end walls of said chambers.

12. The combination according to claim 11,

in whlich the bulkheads are formed of a thermosetting plastic material.

13. The combination according to claim 11, in

which the bulkheads are formed of a graphitic material.

14. The combination according to claim 11, in which the bulkheads are formed of a thermosetting hardened graphitic material.

15. In combination, a rotary fluid mechanism comprising toothed displacement members, one within and eccentric to the other and having teeth differing in number by two, forming rotor chambers between them, sealed from each other during rotation by continuous tooth driving contacts and fluid tight tooth engagements while performing fluid displacement functions during fluid intake and outlet, and a bulkhead moulded to the teeth of each rotor, said bulkheads forming end walls of said rotor chambers, each bulkhead during variations of displacement being slidable with respect to its rotor, each bulkhead having radially projecting portions of molded graphite plastic composition fitting the teeth of its rotor and traveling axially with relation to the other rotor to vary the displacement, said bulkheadsiorming the end walls of said chambers, radial holes thru a displacement member, one from each of its rotor chambers, located to connect said rotor chambers in all positions of varied displacement to ports in said mechanism, said ports being located to register with said holes in all positions of axial travel during variations of displacement.

16. In combination, a rotary fluid mechanism comprising toothed displacement members, one within and eccentric to the other and having teeth difiering in number by at least one, forming rotor chambers between them, said rotor chambers being sealed from each other during rotation by continuous tooth driving contacts at full mesh and pressure holding tooth engagements elsewhere while performing displacement functions during fluid intake and outlet, ports for the intake and outlet of the fluids, and a bulkhead moulded to the teethof each rotor, said bulkheads forming end walls of said rotor chambers, each bulkhead being slidable with respect to its rotor, each bulkhead halving radially projecting portions of thermoset graphite plastic fitting tightly to said teeth and slidable on them, traveling axially to vary the distance between said bulkheads, said [bulkheads forming the end walls of said chambers.

17. In combination, in a casing, a fluid mech- 14 thru a rotor for said intake and outlet of fluid, an individual plastic bulkhead molded to the teeth of each rotor, one bulkhead being axially slidable with respect to its rotor, and the other rotor traveling axially to vary the distance between said bulkheads, said bulkheads forming end walls of said chambers, the displacement of said chambers being variable from maximum to zero.

19. In combination, in a casing, a fluid mechanism comprising toothed displacement members, one within and eccentric to the other and having teeth diil'ering in number by at least one, said teeth. forming rotor chambers between them, said chambers being sealed from each other during rotation by continuous driving and fluid pressure holding tooth engagements while perform-' ing displacement functions during fluid intake and outlet, passageways for the intake and outlet of fluids radially thru one of said rotors, an individual bulkhead molded to the teeth of each rotor ports in said casing registering with said passageways during variations between said bulkheads, said bulkheads forming end walls of said rotor chambers, each bulkhead being axially slidable with respect to its rotor, to vary the distance between them, said bulkheads varying the displacement of said chambers between maximum anism comprising toothed displacement members,

one within and eccentric to the other and having teeth differing in number by at least one, said teeth forming rotor chambers between them, said rotor chambers being sealed from each other during rotation by continuous tooth driving contacts in the full mesh region and fluid pressure holding engagements elsewhere while performing displacement functions during intake and outlet, passageways thru a rotor for the intake and outlet of the fluids radially through the outer rotor, and parts in said casing registering with said passageways and an individual bulkhead of a plastic graphite composition moulded to the teeth of each rotor, said bulkheads forming end walls of said rotor chambers, each bulkhead being slidable with respect to its rotor and one bulkhead traveling axially to vary the displacement distance between said bulkheads.

18. In combination, a fluid mechanism comprising toothed displacement members, one within and eccentric to the other and having teeth differing in number by at leastone, said teeth forming rotor chambers between them, said chambers being sealed from each other during rotation by continuous driving tooth contacts in the full mesh region and fluid tight engagement elsewhere thus performing displacement functions during fluid intake and outlet, passageways and zero, a journal bearing around the outer rotor, the friction resistance of said journal and of the pressure angles of said tooth contacts being adjusted to provide low torque in starting said mechanism.

MYRON I". HILL. FRANCI8 A. JOHN L. CHAPIN, Jn.

REFERENCES CITED The following references are of record in the flle of this patent:

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